fix proxy channels noarch and gzip repodata

[wolfv]

@janjagusch this fixes the noarch issue for proxy channels and also adds the same gzip mechanism we use with regualr channels which should speed up repodata retrieval substantially (if you're not encoding the stream elsewhere anyways).

Let me know what you think.

[wolfv]

aaand there are a couple unrelated changes ... one sec :)

[janjagusch]

aaand there are a couple unrelated changes ... one sec :)

should i wait for CI to go ✅ before reviewing this?

[wolfv]

@janjagusch looks like the CI issue is unrelated. Looking into that now.

[wolfv]

This should be green now.

[codecov-commenter]

Codecov Report

Merging #529 (f094ab2) into main (f094ab2) will not change coverage.
The diff coverage is n/a.

❗ Current head f094ab2 differs from pull request most recent head 8d5187d. Consider uploading reports for the commit 8d5187d to get more accurate results

@@           Coverage Diff           @@
##             main     #529   +/-   ##
=======================================
  Coverage   83.15%   83.15%           
=======================================
  Files          78       78           
  Lines        5919     5919           
=======================================
  Hits         4922     4922           
  Misses        997      997           

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[janjagusch]

thanks for this!